The present invention generally relates to medical devices and, more particularly, to improved temperature control mechanisms for cautery devices using heat pipes.
Medical treatments today often require that areas of organic tissue be cauterized or coagulated quickly, efficiently, and safely during the course of a surgical procedure. For example, surface tissue on a highly vascularized organ such as the human liver or brain may be cauterized immediately following the making of a surgical incision in order to prevent excessive bleeding. Alternatively, retinal tissue in a human eye may be photocoagulated during opthalmic surgery to correct injury or, skin tissue on a human scalp may be coagulated during hair transplant surgery to prevent bleeding resulting from graft incisions. Many prior art devices have been developed to perform cauterization or coagulation as appropriate for such varied applications. Known devices range from simple-direct-contact cauteries, employing a heated wire element to burn or sear relatively large areas of tissue, to more complex laser photocoagulators using highly coherent, monochromatic laser light to perform pin-point coagulation of delicate tissue.
Typically, electrical energy is applied to the tissue being treated so as to cause local heating of the tissue. By varying the power output and the type of electrical energy, it is possible to control the extent of heating and thus the resulting surgical effect. Electrosurgery is often accomplished through the delivery of radio-frequency (RF) current through body tissue to raise the tissue temperature for cutting, coagulating, and desiccating. RF energy in the range of about 500 kilohertz to 1 megahertz, with about 30-watt to 40-watt power levels is typical of electrosurgical generators.
While tissue heating is the mechanism by which the various cautery surgical treatments are effected, it can also cause nonefficacious effects. Total body temperatures above 41.8xc2x0 C. (107.2xc2x0 F.) are detrimental to the functions of the central nervous system, heart, brain, liver, and kidneys, and may even cause histologically obvious damage to tissue cells, whereas, e.g., tumorcidal effects are generally not observed below 42.5.degree. C. (108.5xc2x0 F.). At brain temperatures of over 41.8xc2x0 C. (107.2xc2x0 F.), the mechanism that regulates body temperature can become incapacitated, and there is danger of xe2x80x98malignantxe2x80x99 or xe2x80x98runawayxe2x80x99 hyperthermia. Further, temperatures of up to 45xc2x0 C. (113.0xc2x0 F.) may cause soft tissue necroses and fistulas as well as skin bums. Therefore, accurate temperature control of a localized area is critical to successful cauterization.
As a consequence, surgeons often operate prior electrosurgical devices at a very low power level. This prevents the electrode and the adjacent tissue from becoming too hot, too fast. Unfortunately, it also requires the surgeon to perform the procedure much more slowly than he would if he could operate the device at full power. As a result, the procedure takes much longer, requiring more operating room time.
It has been recognized that cooling the surgical site during electrosurgery is desirable. Several prior art systems have been developed which flush the surgical site with fluid during surgery or transfer the excess heat quickly away from the surgical site. One known apparatus which is used to remove heat from a surgical environment is a xe2x80x9cheat pipexe2x80x9d.
A heat pipe is an elongated tube having a wick running through its length with one end of the tube being in the hot environment and the other end being in a cooler or cold environment. The tube is charged with a selected amount of liquid, known as a xe2x80x9cworking fluid,xe2x80x9d having a particular boiling point such that the liquid will boil in the hot environment and give off vapors which will travel through the tube into the colder environment. In the colder environment the vapors condense back into liquid form and give up thermal energy through the latent heat of condensation. The condensed liquid is then soaked up by the wick and transferred through the wick by capillary action back to the hotter environment where the evaporating cycle is repeated. Such heat pipes can be very efficient so long as there is a difference in temperature between the hot environment and the cool environment.
For example, in U.S. Pat. Nos. 5,647,871, 6,074,389, and 6,206,876, issued to Levine et al., an electrosurgical device, system and a method of electrosurgery are disclosed in which electrosurgical electrodes are cooled by a heat pipe. The device includes at least one electrode for applying the required electrical energy to tissue at a surgical site. During surgery, an internal cavity within the electrode forms a heat pipe heat transfer device. The electrode is closed at both is proximal and distal ends. The cavity within each electrode is evacuated and contains a working fluid, e.g., water. When the distal end of an electrode contacts tissue heated by the electrosurgical procedure, the working fluid inside the electrode evaporates, filling the internal cavity with vapor. At the proximal end of exchanger in the form of external heat conductive fins are used to carry heat away from the device. It should be noted that Levine""s heat pipe assembly is one piece that requires complete immersion of the utensil in a sterilization system for cleaning, thus reducing it""s working life.
In U.S. Pat. No. 5,908,418, issued to Dority et al., a hand held coagulating device is disclosed having a cooled handle for improved user comfort. An outer shell houses internal components of the device and provides a surface for the user to hold the device during a surgical procedure. A contact element positioned in an opening in a forward end of the shell is placed against an area of tissue to be coagulated, and radiation produced by a radiation source, such as an incandescent lamp, is transmitted through the contact element to the tissue. A heat sink is positioned in an opening in an aft end of the shell for conducting heat to the surrounding environment. A heat pipe is connected between the radiation source and the heat sink so that heat is transferred directly from the radiation source to the outside air while the surface used for holding the device remains cool.
There has been a long felt need for an improved cautery tool having a more efficiently designed and effective heat pipe cooling system.
The present invention provides a cautery surgical device comprising a surgical forceps including a pair of elongate arms each including a free end supporting an electrode tip for applying electrical energy to tissue. The arms of the surgical forceps are joined at another end so as to provide for resilient compressible movement of the arms between a normally open position, wherein the arms are disposed in aligned, substantially parallel, spaced-apart relation and a squeezed closed position, wherein the electrode tips are disposed in abutting relationship. The arms of the surgical forceps further include respective spaced-apart free ends and a receptacle extending along each arm from the free end toward the joined end. A heat pipe is releasably mounted to each arm for conducting heat away from the electrode tip. Each heat pipe comprises an evaporator portion having an end and a first diameter, with the electrode tip mounted to the evaporator end. A condenser portion of the heat pipe is spaced away from the evaporator end, and advantageously transitions from the first diameter to at least one smaller diameter section. In a preferred embodiment of the invention, the heat pipe further includes a cylindrical tube having an evaporation end, a condensation end, and a central passageway that is lined with a wick and at least partially filled with a fluid. The condensation end comprises a diameter that is smaller than the diameter of the evaporation end so as to be releasably received within a socket disposed within the receptacle of each arm. The socket includes a longitudinal blind hole that is sized so as to releasably receive the smaller diameter section of the condenser portion and a catch for engaging a portion of the arm.